Cape Peninsula
The endemic flora of the Cape Peninsula
Many of the plants that grow in this well-known plant and people hotspot are found in this small area and nowhere else.
by Nick Helme, Nick Helme Botanical Surveys, and Terry Trinder-Smith, Bolus Herbarium, University of Cape Town
The Cape Peninsula is an area of exceptional plant diversity, yet no list of the 161 endemic plant taxa that occur here has ever been puplished. We decided to set this right*. To start, we defined the Cape Peninsula as the area west of a line connecting Paarden Island to Muizenberg, including a small part of the western edge of the area known as the Cape Flats. The area is characterized by the presence of the Cape Peninsula mountain chain and this extends from Signal Hill and Lion's Head in the north to Cape Point in the south. The total land area is 471 km2 (47 100 hal and some 24 000 ha are now formally or contractually conserved within the Table Mountain National Park, which includes 80% of the actual mountain chain. Studies of this nature are bedeviled by taxonomic (see glossary) revisions and TOP: View of the Peninsula mountain chain from changes (particularly in the genera Erica, eliffonia and the mesembs) but about Klawer Valley above Simon's Town, with Table 2 285 plant species are known to be indigenous to the Cape Peninsula, which Mountain in the distance and winter fog covering the Cape Flats and the lowlands surrounding False means that the Peninsula has the greatest concentration of plant species (per unit Bay. area) within the Cape Floristic Region. What makes this even more remarkable is that 161 (158 species and three subspecies) of these are found nowhere else and ABOVE: Staavia dodii. Photos: Nick Helme, are thus regarded as being endemic. This concentration of endemic species is high for a continental area, but is substantially exceeded by various island floras.
114 September 2005 Veld&Flora A profile of the endemic flora with a remarkable 31% of this genus endemic to the Peninsula. What is The figure of 161 endemic 'taxa' (see endemic to the Peninsula, and the area interesting about this is that many of glossary on page 117 for a reminder can thus be regarded as a major cen these genera are well represented on of the meanings of the confusing tre of endemism for Roella. Muralria, the Peninsula (they are relatively spe terminology of taxonomy) includes Tetraria and Serruria all have about cies-rich), yet their centres of endemism three subspecies, and is made up of 10% of their total species endemic to lie further afield. In other words, the twenty-seven families#. The ten families the Peninsula, and likewise this is Peninsula is not a critical area for the on the Cape Peninsula with the largest something of a centre of endemism for conservation of species diversity within numbers of endemic species within these genera. these genera. them are the Ericaceae with thirty Even more noticeable is the signifi nine species, the Fabaceae (legumes) cant under-representation of endemic Hotspots on the Peninsula with nineteen species, the Cyperaceae species in certain large genera, such Distribution of endemic plant species with eleven, the Asteraceae (daisies), as Agathosma, Phylica, Aspalathus, on the Peninsula does not appear to be Campanulaceae, Iridaceae, Polygalaceae Pelargonium, Oxalis, Cli/jortia, Moraea, random, and all areas are not equally and the Proteaceae all with ten, the Senecio, Thesium and Crassula. In all blessed with localized species. In some Restionaceae with seven and the these cases less than 2% of the total places we have recorded up to eight Aizoaceae# (mesembs) with six endemic number of species in the genus is Peninsula endemics growing within a species. Each family is grouped into genera, and the genera are further divided into species (see glossary). Some of the families in the Top Ten list mentioned above are dominated by a single genus with lots of species (as in the Ericaceae), and others have a number of genera each further divided into species (as in the Restionaceae). Families with lots of endemic species on the Cape Peninsula include the Ericaceae, Campanulaceae, Cyperaceae, Polygalaceae and Proteaceae. Some families have no endemic species on the Cape Peninsula (the Geraniaceae, Oxalidaceae, Thymelaeaceae, Poaceae and Apiaceae), while others are represented by a few: the huge daisy family has only ten endemic species in this area, the Hyacinthaceae and Rhamnaceae have one each, the Rutaceae two and the ABOVE: Mimetes fimbriifolius is a Cape Peninsula endemic and one of the largest members of the Proteaceae Orchidaceae three. in the south-western Cape. Indeed, with its height and thick protective bark - adaptations to survive fire - it Nine genera contain most of the of can be regarded as an 'honorary' tree. Cape Peninsula endemics, these being BELOW: Staavia dodii is endemic to a small, lowland area of about 100 ha near the southern tip of the Cape Peninsula, overlooking the cool Atlantic Ocean. It belongs to the Bruniaceae, afamily endemic to the Cape Erica with thirty-nine, Muraltia with Floristic Region, bar one very rare outlier species in Pondoland, Raspalia trigyna. ten, Aspalathus with seven, Roella Photos: Nick Helme. with six, Indigojera and Serruria both with five, and Gladiolus, Tetraria and Leucadendron with four species each. The representation of endemic species within the Cape Peninsula appears to be heavily skewed in favour of a few genera, with only six genera accounting for 45% of the endemic species. Erica is a peculiar case as this enormous genus (containing almost 700 species) is species-rich in most areas where the climate is not extreme and the topography fairly variable, with many endemics in such areas. Only 6% of the Erica species ofthe Cape Floristic Region are endemic to the Cape Peninsula, but in terms of sheer numbers of endemic species this genus is by far the 'Iargest with thirty-nine endemics. The standout genus is clearly Roella, 30m2 area! Interestingly, there is a to be endemic to the richer shale and of Stellenbosch (as Gladiolus pappei, strong correlation between the distri granite soils that are prevalent on the recently confirmed from the latter area, butions of endemic animals (primarily lower slopes of the northern part of testifies). This link is perhaps main invertebrates) and endemic plants on the Peninsula, perhaps because these tained by high rainfall and summer the Peninsula, and this is especially habitats are better represented further cloud incidence in these areas that are true on Table Mountain itself. to the east. separated by 60 kIn of intervening Cape Concentrations of endemic plants Numerous species occur only on Flats (at an elevation of no more than occur on the few remaining examples of the Peninsula and then again on the 100 m), which was largely under the sand plain fynbos within the Peninsula, southern coastal Hottentots Holland sea four million years ago. notably within the conservation area Mountains between Rooiels and at Kenilworth Racecourse and at Kleinmond, providing strong evidence Conservation Zandvlei and Rondevlei Reserves (the that these areas were once linked when At least sixty-six (41%) of the latter just outside the study area). sea levels were lower. There is also Peninsula's endemic species are cur This concentration is probably artificial, a notable link between the flora of rently Red Data Book listed as threat in that once widespread Cape Flats Table Mountain and the higher moun ened in some way, and are thus of species are now restricted to remnant tains above Jonkershoek, just east immediate conservation concern. Many conservation areas. Other notable hotspots of endemics include most of Table Mountain, Karbonkelberg, Constantiaberg, Noordhoek Peak, the RIGHT: Serruria decumbens (Proteaceae) is a curious creeping member of the Serruria Kalk Bay plateau, Rooikrans hill above genus, endemic to relatively low altitude, Capri, the Klawer valley wetlands above rocky areas on the southern tip of the Cape Simon's Town, the Swartkop mountains Peninsula. above Millers Point and most of the BELOW: Erica halicacaba is avery unusual Cape of Good Hope Nature Reserve area. member of the largest genus is the Cape The latter area supports no less than Floristic Region. Its robust flowers have a very narrow opening and it is not known eleven endemics, with another species what pollinates them. restricted to the area immediately adjacent. Key habitats for endemics OPPOSITE: Aloe commixta (Asphodelaceae) and, in the background, Aspalathus capensis include seepage areas and wetlands, (Fabaceae) are endemic to the southern steep, moist south or south-east facing Cape Peninsula, growing in areas with slopes (many of which receive summer shallow acidic sands and outcropping sand stones. Photos: Nick Helme. moisture in the form of cloud) and lower rocky sandstone slopes in the southern Peninsula. Relatively few species seem BotSoc link are extremely localized, and in some National Park is extremely fortuitous cases are known from a single popula given the global conservation signifi TO DISCOVER more about the rich flora of the tion of fewer than fifty plants, and these cance of this area, and its future looks Table Mountain National Park, consult Mary are obviously in imminent danger of relatively bright. The main concerns Maytham Kidd's Cape Peninsula, South African extinction. Seven Peninsula endemics for the endemic species in the Park are Wild Flower Guide 3, published by the Botanical are already confirmed extinct, with only inappropriate fire regimes (too far apart, Society but beware of the fact that it is out of one of these, Erica verticillata, in culti or too frequent), alien invasive species, date and many names have changed. For more detail, see The Levyns Guide to the Plant Genera vation. A further seven species are like random events such as disease and of the Southwestern Cape by Terry Trinder ly to be extinct as they have not been plant collecting (for the rarest species) Smith. These books are available at the Botanical collected for at least thirty years, and in and, more difficult to detect, the long Society Bookshop at Kirstenbosch (for details some cases for over a century. Most of term loss of genetic diversity and key see p. 148). the extinct species are lowland plants pollinators. Urbanization pressures and whose habitats have now been trans lack of motivated and skilled manage formed by agriculture and urbanization, ment continue to be a major threat to Table Mountain's endemic invertebrates and the main 'extinction hotspot' is the the lowland areas outside the National THE WORLD Wide Fund for Nature's Table western edge of the Cape Flats (incorpo Park. ~ Mountain Fund (WWF) has recently awarded rating acid sands, shales and granites) a grant to James Pryke, a Ph.D. student in from Paarden Island to Kenilworth and
WHAT DOES THAT MEAN?
Cape Floristic Region One of the world's richest temperate areas in terms of botanical diversity, encompassing the Cape Peninsula and other winter rainfall parts of the N, Wand E Cape. endemic A species occurring in one particular area and nowhere else. genus A rank in the taxonomic hierarchy, subor dinate to family, but above the rank of species. All plants (indeed all liVing organisms) are given a Latin name in two parts: the binomial. The genus is the first part of the binomial, with the species (or specific epithet if you want to sound posh) making up the other half. For example, the king protea's Latin name is Protea cynaroides, which is made up of the generic name of Protea and the specific name of cynaroides. species The main unit of study in taxonomy, it is agrouping of all the populations of one breeding group that are separated from other such groups Acknowledgements by marked differences. It is the second part of Various specialists who made their information available to us, and the staff of the Compton Herbarium, the binomial (its Latin name). Kirstenbosch, for access to their collections. taxon (plural taxa) A taxonomic group of any rank - order, family, genus, species or subspe Further reading cies. taxonomy The study of the principles and prac Biodiversity and Conservation, vol. 5, 1996. A special edition dedicated to the biodiversity of the Cape Peninsula tices of the classification of the natural world, with numerous relevant papers. which includes systematics (the study and Goldblatt, P. and Manning, J. 2000. Cape Plants: Aconspectus of the Cape flora of South Africa. Stre/itzia, 9. description of the variation in living organisms Pauw, A. and Johnson, S. 1999. Table Mountain: a natural history. Fernwood Press, Cape Town. and the relationships that exist between them).
September 2005 Veld&Flora 117